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- /* Reading symbol files from memory.
- Copyright (C) 1986-2022 Free Software Foundation, Inc.
- This file is part of GDB.
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- /* This file defines functions (and commands to exercise those
- functions) for reading debugging information from object files
- whose images are mapped directly into the inferior's memory. For
- example, the Linux kernel maps a "syscall DSO" into each process's
- address space; this DSO provides kernel-specific code for some
- system calls.
- At the moment, BFD only has functions for parsing object files from
- memory for the ELF format, even though the general idea isn't
- ELF-specific. This means that BFD only provides the functions GDB
- needs when configured for ELF-based targets. So these functions
- may only be compiled on ELF-based targets.
- GDB has no idea whether it has been configured for an ELF-based
- target or not: it just tries to handle whatever files it is given.
- But this means there are no preprocessor symbols on which we could
- make these functions' compilation conditional.
- So, for the time being, we put these functions alone in this file,
- and have .mt files reference them as appropriate. In the future, I
- hope BFD will provide a format-independent bfd_from_remote_memory
- entry point. */
- #include "defs.h"
- #include "symtab.h"
- #include "gdbcore.h"
- #include "objfiles.h"
- #include "gdbcmd.h"
- #include "target.h"
- #include "value.h"
- #include "symfile.h"
- #include "observable.h"
- #include "auxv.h"
- #include "elf/common.h"
- #include "gdb_bfd.h"
- #include "inferior.h"
- /* Verify parameters of target_read_memory_bfd and target_read_memory are
- compatible. */
- gdb_static_assert (sizeof (CORE_ADDR) >= sizeof (bfd_vma));
- gdb_static_assert (sizeof (gdb_byte) == sizeof (bfd_byte));
- gdb_static_assert (sizeof (ssize_t) <= sizeof (bfd_size_type));
- /* Provide bfd/ compatible prototype for target_read_memory. Casting would not
- be enough as LEN width may differ. */
- static int
- target_read_memory_bfd (bfd_vma memaddr, bfd_byte *myaddr, bfd_size_type len)
- {
- /* MYADDR must be already allocated for the LEN size so it has to fit in
- ssize_t. */
- gdb_assert ((ssize_t) len == len);
- return target_read_memory (memaddr, myaddr, len);
- }
- /* Read inferior memory at ADDR to find the header of a loaded object file
- and read its in-core symbols out of inferior memory. SIZE, if
- non-zero, is the known size of the object. TEMPL is a bfd
- representing the target's format. NAME is the name to use for this
- symbol file in messages; it can be NULL. */
- static struct objfile *
- symbol_file_add_from_memory (struct bfd *templ, CORE_ADDR addr,
- size_t size, const char *name, int from_tty)
- {
- struct objfile *objf;
- struct bfd *nbfd;
- struct bfd_section *sec;
- bfd_vma loadbase;
- symfile_add_flags add_flags = SYMFILE_NOT_FILENAME;
- if (bfd_get_flavour (templ) != bfd_target_elf_flavour)
- error (_("add-symbol-file-from-memory not supported for this target"));
- nbfd = bfd_elf_bfd_from_remote_memory (templ, addr, size, &loadbase,
- target_read_memory_bfd);
- if (nbfd == NULL)
- error (_("Failed to read a valid object file image from memory."));
- /* Manage the new reference for the duration of this function. */
- gdb_bfd_ref_ptr nbfd_holder = gdb_bfd_ref_ptr::new_reference (nbfd);
- if (name == NULL)
- name = "shared object read from target memory";
- bfd_set_filename (nbfd, name);
- if (!bfd_check_format (nbfd, bfd_object))
- error (_("Got object file from memory but can't read symbols: %s."),
- bfd_errmsg (bfd_get_error ()));
- section_addr_info sai;
- for (sec = nbfd->sections; sec != NULL; sec = sec->next)
- if ((bfd_section_flags (sec) & (SEC_ALLOC|SEC_LOAD)) != 0)
- sai.emplace_back (bfd_section_vma (sec) + loadbase,
- bfd_section_name (sec),
- sec->index);
- if (from_tty)
- add_flags |= SYMFILE_VERBOSE;
- objf = symbol_file_add_from_bfd (nbfd, bfd_get_filename (nbfd),
- add_flags, &sai, OBJF_SHARED, NULL);
- current_program_space->add_target_sections (objf);
- /* This might change our ideas about frames already looked at. */
- reinit_frame_cache ();
- return objf;
- }
- static void
- add_symbol_file_from_memory_command (const char *args, int from_tty)
- {
- CORE_ADDR addr;
- struct bfd *templ;
- if (args == NULL)
- error (_("add-symbol-file-from-memory requires an expression argument"));
- addr = parse_and_eval_address (args);
- /* We need some representative bfd to know the target we are looking at. */
- if (current_program_space->symfile_object_file != NULL)
- templ = current_program_space->symfile_object_file->obfd;
- else
- templ = current_program_space->exec_bfd ();
- if (templ == NULL)
- error (_("Must use symbol-file or exec-file "
- "before add-symbol-file-from-memory."));
- symbol_file_add_from_memory (templ, addr, 0, NULL, from_tty);
- }
- /* Try to add the symbols for the vsyscall page, if there is one.
- This function is called via the inferior_created observer. */
- static void
- add_vsyscall_page (inferior *inf)
- {
- struct mem_range vsyscall_range;
- if (gdbarch_vsyscall_range (inf->gdbarch, &vsyscall_range))
- {
- struct bfd *bfd;
- if (core_bfd != NULL)
- bfd = core_bfd;
- else if (current_program_space->exec_bfd () != NULL)
- bfd = current_program_space->exec_bfd ();
- else
- /* FIXME: cagney/2004-05-06: Should not require an existing
- BFD when trying to create a run-time BFD of the VSYSCALL
- page in the inferior. Unfortunately that's the current
- interface so for the moment bail. Introducing a
- ``bfd_runtime'' (a BFD created using the loaded image) file
- format should fix this. */
- {
- warning (_("Could not load vsyscall page "
- "because no executable was specified"));
- return;
- }
- std::string name = string_printf ("system-supplied DSO at %s",
- paddress (target_gdbarch (),
- vsyscall_range.start));
- try
- {
- /* Pass zero for FROM_TTY, because the action of loading the
- vsyscall DSO was not triggered by the user, even if the
- user typed "run" at the TTY. */
- symbol_file_add_from_memory (bfd,
- vsyscall_range.start,
- vsyscall_range.length,
- name.c_str (),
- 0 /* from_tty */);
- }
- catch (const gdb_exception &ex)
- {
- exception_print (gdb_stderr, ex);
- }
- }
- }
- void _initialize_symfile_mem ();
- void
- _initialize_symfile_mem ()
- {
- add_cmd ("add-symbol-file-from-memory", class_files,
- add_symbol_file_from_memory_command,
- _("Load the symbols out of memory from a "
- "dynamically loaded object file.\n"
- "Give an expression for the address "
- "of the file's shared object file header."),
- &cmdlist);
- /* Want to know of each new inferior so that its vsyscall info can
- be extracted. */
- gdb::observers::inferior_created.attach (add_vsyscall_page, "symfile-mem");
- }
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